Process of coating metal substrates with silicone elastomer

ABSTRACT

A composition of a vinyldiorganosiloxy endblocked polydimethylsiloxane and a mixture of an organosiloxane having five to 20 silicon atoms per molecule and an average of at least three silicon-bonded hydrogen atoms per molecule and a modified organosiloxane having six to 21 silicon atoms per molecule, an average of at least two silicon-bonded hydrogen atoms per molecule and an average of at least one unit of (RO)3Si(CH2)x(CH3)SiO, (RO)3Si(CH2)x(CH3)2SiO0.5 and mixtures thereof where R is methyl, ethyl or   AND X IS 2 OR 3 IS CURABLE TO AN ELASTOMER WHICH HAS IMPROVED UMPRIMED ADHESION TO SUBSTRATES, PARTICULARLY METAL SUBSTRATES.

United States Patent [191 Clark et al.

[ Nov. 13, 1973 PROCESS OF COATING METAL SUBSTRATES WITH SILICONE ELASTOMER [75] Inventors: William H. Clark, Mt. Pleasant;

William R. Hays, Midland, both of [21] Appl. No.: 255,900

[52] US. Cl 117/132 BS, 117/161 ZA, 117/232 [51] Int. Cl B4411 1/36, CO9d 3/82 [58] Field of Search 117/132 BS, 161 ZA,

117/232; 260/37 SB, 46.5 G, 46.5 UA

[561 References Cited UNITED STATES PATENTS 3,627,851 12/1971 Brady 117/132 BS 3,696,068 10/1972 Creamer 3,697,473 10/1973 Polmanteer et al. 260/37 SB 3,527,655 9/1970 Ballard 260/465 UA 3,647,917 3/1972 Schulz et al. 260/465 G X Primary Examiner-Murray Katz Assistant Examiner-Harry J. Gwinnell Attorney-Robert F. Fleming, Jr. et al.

[57] ABSTRACT A composition of a vinyldiorganosiloxy endblocked polydimethylsiloxane and a mixture of an organosiloxane having five to 20 silicon atoms per molecule and an average Of at least three silicon-bonded hydrogen atoms per molecule and a modified organosiloxane having six to 21 silicon atoms per molecule, an average of at least two silicon-bonded hydrogen atoms per molecule and an average of at least one unit of (RO) Si(CH )x(CH )SiO, (R0) Si(CH )X(CH SiO and mixtures thereof where R is methyl, ethyl or O CHAS-- and x is 2 or 3 is curable to an elastomer which has improved umprimed adhesion to substrates, particularly metal substrates.

4 Claims, No Drawings PROCESS OF COATING METAL SUBSTRATES WITH SILICONE ELASTOMER This is a division of application Ser. No. 156,551, filed June 24, 1971 now US. Pat. No. 3,699,072. This invention relates to an organosiloxane composition which is curable to an elastomer which has improved unprimed adhesion to substrates.

The adhesion of silicone elastomers to substrates, such as metals, glass, paper, wood, masonry, stone and the like is of significant importance to the spectrum of utility of the silicone elastomer. Although some silicone elastomers adhere to some substrates, not all silicone elastomers adhere to all substrates. Furthermore, those silicone elastomers which do adhere to some substrates often have adhesive strengths which limit their utility. One method of gaining improved adhesion to various substrates is to prime the surface. This procedure although often effective has the disadvantage that the user is required to apply two compositions. This is time consuming, inconvenient and in general more expensive. Therefore, to avoid the use of a primer, the elastomer composition can be formulated to provide the necessary adhesion without the use of primers. The addition of ingredients to elastomer formulations is not without problems, since some ingredients can destroy the elastomeric properties, inhibit cure and the like. The composition of this invention does not interfere with the elastomer in any way and still provides improved adhesion to substrates.

It is therefore an object of this invention to provide a siloxane composition which can be cured to an elastomer having improved unprimed adhesion to substrates. This object and others will become apparent from the following detailed description of the present invention.

This invention relates to a curable composition consisting essentially of (l) a vinyldiorganosiloxy endblocked polydimethylsiloxane having a viscosity of from 1,000 to 100,000 cs. at 25C. wherein the organic groups of the vinyldiorganosiloxy units are selected from the group consisting of methyl and phenyl, (2) a mixture consisting essentially of (a) an organosiloxane having an average of from 5 to 20 inclusive silicon atoms per molecule, organosiloxane units bonded together through silicon-oxygen-silicon bonds and selected from the group consisting of dimethylsiloxane units and methylhydrogensiloxane units and endblocked with organosiloxane units selected from the group consisting of trimethylsiloxane units and dimethylhydrogensiloxane units, there being present an average of at least three silicon-bonded hydrogen atoms per molecule and (b) a modified organosiloxane having an average of from six to 21 silicon atoms per molecule, organosiloxane units bonded together through silicon-oxygen-silicon bonds selected from the group consisting of dimethylsiloxane units, methylhydrogensiloxane units and (RO) Si(CH ,(CH )SiO units wherein R is a monovalent radical selected from the group consisting of methyl, ethyl and and x is an integer of from 2 to 3 inclusive, and endblocked with organosiloxane units selected from the group consisting of trimethylsiloxane units, dimethylhydrogensiloxane units and (R0) Si(Cl-l ),,(Cl-l ),,SiO,, units, there being present an average of at least two silicon-bonded hydrogen atoms per molecule and an average of one siloxane unit selected from the group consisting of (RO);,. Si(Cl-l ),(CH )SiO units and (RO) Si(Cl-l ),(CH ),SiO units, said mixture (2) being present in an amount sufficient to provide at least one siliconbonded hydrogen atom per vinyl radical in (l) and not more than 10 silicon-bonded hydrogen atoms per vinyl radical in (1), said mixture having present from 15 to mol percent modified organosiloxane (b) where (a) and (b) are mol percent.

The vinyldiorganosiloxy endblocked polydimethylsiloxanes (l) are well known in the art. These polydimethylsiloxanes can have viscosities of from 1,000 to 100,000 cs. at 25C., preferably 2,000 to 60,000 cs. at 25C. The organic groups of the vinyldiorganosiloxy units can be methyl or phenyl.

The mixture (2) is a crosslinking agent which in the composition of this invention, enhances the adhesion of the silicone elastomer to substrates without the use of primers. Mixture (2) is a combination of (a) an organosiloxane having five to 20 silicon atoms per molecule and at least three silicon-bonded hydrogen atoms and (b) a modified organosiloxane having six to 21 silicon atoms and at least two silicon-bonded hydrogen atoms and an average of one siloxane unit of the formula )a( 2).r( a) )a z)I( 3)2 o.5 or mixtures thereof.

organosiloxane, (a),"contains at least three siliconbonded hydrogen atoms per molecule and from five to 20 silicon atoms per molecule. The organosiloxane contains organosiloxane units bonded through siliconoxygen-silicon bonds where the units can be dimethylsiloxane units and methylhydrogensiloxane units and endblocking units of trimethylsiloxane and dimethylhydrogensiloxane. The organosiloxane contains combinations of the above siloxane units such that there are at least three silicon-bonded hydrogen atoms per molecule and five to 20 silicon atoms per molecule. The organosiloxanes (a) can be illustrated by a copolymer containing two units of trimethylsiloxane, five units of methylhydrogensiloxane and three units of dimethylsiloxane, a copolymercontaining two units of dimethylhydrogensiloxane, three units of methylhydrogensiloxane and five units of dimethylsiloxane, a copolymer of two units of trimethylsiloxane, seven units of methylhydrogensiloxane and eleven units of dimethylsiloxane, a copolymer of two units of trimethylsiloxane and eighteen units of methylhydrogensiloxane, a copolymer of two units of trimethylsiloxane and three units of methylhydrogensiloxane, and a copolymer of two untis of dimethylhydrogensiloxane, ten units of methylhydrogensiloxane and two units of dimethylsiloxane. The number of siloxane units in the copolymers are the avcrage number per molecule. The organosiloxanes (a) are well known in the art.

The modified organosiloxanes (b) are the organosiloxanes of (a) wherein some of the silicon-bonded hydrogen atoms have been replaced by (RO) Si(CH,), R is methyl, ethyl or and xis 2 or 3. Therefore, organosiloxane (b) contains one more silicon atom per molecule than its precurser and the average number of silicon atoms per molecule is six to 21. The modified organosiloxane (b) therefore contains organosiloxane units selected from dimethylsiloxane units, trirnethylsiloxane units, methylhydrogensiloxane units, dimethylhydrogensiloxane units (R Si(Cl-l ),(CH )SiO units and (R0) SKCH,) (Cl-l SiO units. The organosiloxane (b) contains an average of at least two units having silicon-bonded hydrogen atoms and an average of one unit of (RO) Si(CH (Cl-l )SiO, (RO) Si(CH ),(CH SiO and mixtures thereof. The following copolymers illustrate the modified organosi loxane (b), a copolymer having an average of one unit of (CH COO) SiCH CH (Cl-l SiO,, one unit of dimethylhydrogensiloxane, four units of diemthylsiloxane and methylhydrogensiloxane, a copolymer having an average of one unit of (Cl'l O) SiCl-l CH (CI-l SiO five units of dimethylsiloxane, three units of methylhydrogensiloxane and one unit of diemthylhydrogensiloxane, a copolymer containing an average of one unit of (CH CH O) SiCl-l Cl-l (CH SiO one unit of dimethylhydrogensiloxane and three units of methylhydrogensiloxane, a copolymer containing an average of one unit of (CI-[ O) SiCH CH Cl1l. (CI-l SiO one unit of dimethylhydrogensiloxane, two units of dimethylsiloxane and two units of methylhydrogensiloxane, a copolymer containing an average of two units of trimethylsiloxane, two units of methylhydrogensiloxane and one unit of (CH COO) SiCl-l Ci-l (Cl-l )SiO, a copolymer containing an average of two units of trimethylsiloxane, one unit of LQH O) SiCH2CH (CH )SiO, four units of methylhydrogensilox an efand three ufiitsof dimethylsilox ane, a copolymer containing an average of two units of dimethylhydrogensiloxane, one unit of (CH CH O) SiCH CH CH,(CH )SiO, two units of methylhydrogensiloxane and five units of dimethylsiloxane and a mixture of a copolymer containing an average of one unit of (CH COO) SiCl-l cl-lflcl-l hsio three units of methylhydrogensiloxane, five units of dimethylsiloxane and one unit of dimethylhydrogensiloxane and a copolymer containing an average of two units of dimethylhydrogensiloxane, two units of methylhydrogensiloxane, one unit of (CH COO) SiCH,CH (Cl-l )SiO and five units of dimethylsiloxane. There may be some molecules of organosiloxane (b) which have two units of the adduct. However, since the ratio of organosiloxane containing the silicon-bonded hydrogen atoms to silane is in favor of only one adduct per molecule, there will not be large amounts of such molecules. The mixture of (a) and (b) can include such amounts allyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, allyltriacetoxysilane molecules with two adducts without departing from the scope of this invention. 2(2) Mixture (2) can be prepared by reacting part of the organosiloxane containing silicon-bonded hydrogen atoms with a silane such as vinyltriacetoxysilane, allyltriacetoxysilane and allytriethoxysilane. The amount of silane used is sufficient to provide to 75 mol percent of modified organosiloxane (b) with the remainder unreacted organosiloxane as defined in (a) and the mixture of (a) and (b) is 100 mol percent. The reaction is best carried out by heating a mixture of organosiloxane having silicon-bonded hydrogen atoms and the silane for l to 2 hours at 140 to 160C. The reaction can be carried out at lower temperatures and in shorter periods of time by heating the reaction mixture in the presence of a platinum catalyst. The use of platinum in preparing the mixture (2) is not preferred when the composition of this invention is to be stored for long periods of time, since the residual platinum catalyst from the preparation of mixture (2) will cause the composition to cure. When a platinum catalyst is used to prepare the mixture and storage of the composition is desired, the platinum catalyst should be removed by careful filtration such as mixing with charcoal and then filtering. However, the platinum need not be removed and the mixture (2) can be added to the vinyldiorganosiloxy endblocked polydimethylsiloxane at the time cure is desired.

The platinum catalyst need not be removed if the composition is to be cured above room temperature, such as above 50 to C. Where a heat cure is desired, the platinum catalyst composition can contain an inhibitor which inhibits cure at room temperature and up to about 50C., however, the composition cures when heated above 50C. Such inhibitors include benzotriazole, stannous salts, mercuric salts, bismuth salts, cuprous salts, cupric salts, acetylenic unsaturated compounds such as Z-ethynylisopropanol and the like.

The composition of this invention can be prepared by mixing the vinyldiorganosilxoy endblocked polydimethylsiloxane with mixture (2) such that there is at least one silicon-bonded hydrogen atom per vinyl radical of the vinyldiorganosiloxy endblocked polydimethylsiloxane. The amount of mixture 2) can be sufficient enough to provide up to ten silicon-bonded hydrogen atoms per vinyl radical of l or more. The higher ratio of silicon-bonded hydrogen atoms to vinyl radical is preferably used when the composition of this invention has a filler present.

The compositions of this invention can be cured by adding a platinum catalyst. The platinum catalyst can be present in catalytic amounts such as 0.5 to 200 parts by weight of platinum per million parts by weight of vinyldiorganosiloxy endblocked polydimethylsiloxane, preferably from 1 to 50 parts by weight of platinum per million parts by weight of the polydimethylsiloxane.

The platinum catalysts are well known and any of the platinum catalysts which are readily dispersible in the composition of this invention are suitable. The platinum catalysts can be illustrated by platinic chlorides, salts of platinum, platinum complexes and chloroplatinic acid, such as PtCl,[P(CH Cl-l,CH platinum bromides, a complex of platinous halide and an olefin -0 tcirnamtcincoon=ccnn,

PtCl CO and PtBr CO.

The composition of this invention can also contain fillers. The fillers are those conventionally used in silicon elastomers either reinforcing such as fume silica or non-reinforcing. The silica fillers can be treated or untreated to make them hydrophobic. Treated fillers are well known in the art and include treatment with chlorosilanes, such as triorganochlorosilanes and diorganodichlorosilanes, diorganocyclosiloxanes, hexaorthe ingredients defined below by heating 1.5 hours at 150C.

A. 30 parts by weight of a copolymer containing an average of two trimethylsiloxane units, three dimethylganodisiloxane,organosilazanes and the like. Examples 5 siloxane units and five methylhydrogensiloxane units of suitable fillers include, fume silica, silica aerogel, siland ica xerogel, silica soot, carbon black, quartz, diatoma- 2.9 parts by weight vinyltriacetoxysilane ceous earth, metal carbonates such as calcium carbon- B. 30 parts by weight of the copolymer defined in (A) ate, metal oxides, such as alumina, metal silicates such above and as zirconium silicate, clays, talc and the like. The 10 4.0 parts by weight allytrimethoxysilane amount of filler can vary broadly from no filler to C. 30 parts by weight of the copolymer defined in amounts such as 200 parts by weight per 100 parts by above and weight of composition deppending upon the filler and 4.0 parts by weight of vinyltriethoxylsilane. Mixture the properties desired. (A) contained modified organosiloxane molecules The compositions of this invention can also contain having an average of one unit of (CH COO) other ingredients conventionally used in silicone elasto- 2 2( a) p molecule and the amount mers such as pigments and dyes to impart color, plastig lh fi efgahosiloxahe in t miXtur was 28 cizers, heat stability additives and the like. mol percent where the unreacted copolymer de- The compositions of this invention can be prepared fined in made P the femaihdef- Mixture by mixing the ingredients by conventional means, such contained modified organosiloxane molecules havas milling, commercial mixers and the like. The order ing an average of one uni of s of mixing is not narrowly critical, however, one conve- SiCH CH CH (CH SiO per molecule and the nient method is to use the base polymer, in this case the m n of m fi rg8n0 X n in the mix re vinyldiorganosiloxy endblocked polydimethylsiloxane, W88 56 "1 pe c t Where h unreacted copolyand the other ingredients are added to it such as filler, defined in made P the l'emaihdefif used, the platinum catalyst and then when cure is delure contained modified organosiloxane having sired mixture (2) is added, an average of one unit of (CH CH O The compositions of this invention are particularly 2 z( a) P molecule and the amount useful as elastomers, potting compounds, coatings, of modified organosiloxane in the mixture was 48 electrical insulation and other uses where silicone elasm0] Percent Where the a t d cop lym r tomers find utility. The compositions of this invention fined in made P the remainderhave an advantage over prior art silicone elastomers in The Silicone elastomer composition was p p y that the composition when cured in contact with a submixing in a eommereial mixer 100 Parts y weight of a strate the cured silicone elastomer has improved adheylphenylvinylsiloxy endblocked polydimethylsion to unprimed surfaces. Composites of silicone elas- SilOXahe having a viscosity of 15,000 at 30 tomers and metal substrates can be obtained by apply- Parts y Weight of a fume Silica filler hydrophobed y ing the composition of this invention with a platinum trimethylsiloxy g p parts y weight of mixture catalyst and thereafter curing the elastomer by heating as defined above, and 20 drops of a above 80C f at least 5 i m l h h h ichloroplatinic acid catlyst. The silicone elastomer comcone elastomer cures at room temperature, heating the 40 position was Cured in test bars for physical property composite enhances the adhesion to the metal submeasurements and was also cured aluminum and strate. The improved adhesion is particularly enhanced Steel Panels for adhesion measurements in accordance where the substrate is a metal such as aluminum or With'ASTM-D'903 Procedure, P Strength The steel. compositions were cured for 15 minutes at 150C. and The following examples are illustrative only and also for one week at o temperature The results should not be construed as limiting this invention which were as h Wh ip Table I m TABLE I Adhesion Aluminum Steel Tensile Elonga- Tear Cure Duromstrength tion at strength Peel Percent Peel Percent Composition with condleter, at break, break, is B, strength, cohesive strength, cohesive mixture tions Shore A p.s.i. percent p.p.l. p.l.i. failure p.l. failure 23 1, 110 887 72 s 0 12. 2 0 30 1,080 827 48 25 0 45 32 880 s07 84 4s 0 30 0 31 1, 180 900 74 122 122 100 28 1,190 920 64 24 0 20 0 30 1, 280 893 53 120 100 120 100 21 1, 240 913 65 24 0 16 0 27 1,200 890 51 60 100 Control was 2.5 parts by weight of the copolymer as defined in (A) above.

2 Room temperature.

is properly delineated in the claims.

EXAMPLE 1 The following mixtures were prepared by reacting a peel strength of 66 p.l.i. with percent cohesive failure and on aluminum had a peel strength of 90 p.l.i. with 100 percent cohesive failure. The silicone elastomer with mixture (C) on steel had a peel strength of 30 p.l.i. with no cohesive failure and on aluminum had a peel strength of 90 p.].i. with 100 percent cohesive failure.

EXAMPLE 2 The following mixtures were prepared by reacting 3O EXAMPLE 3 parts by weight of the copolymer defined in Example 1, (A) with an amount of silane as shown in Table ll by heating for 1.5 hours at 150C. The mol percentage of modified organosiloxane and the adduct unit present in an average of one unit per molecule of modified orpercentage being the unreacted copolymer as defined in Example 1. The modified organosiloxane contained an average of one adduct unit per molecule, the adduct unit corresponding to the silane and present in ratio as the silane was added. The adduct units were as shown The silicone elastomer compositions as described in Example 1 were prepared with the above mixtures (A) through (I) and the physical properties and adhesion properties were determined as described in Example 1. 50 The silicone elastomers in this example were all cured for minutes at 150C. The results were as shown in ganosiloxane was as shown in Table II. In each case the 15 in Table remaining mol percentage was unreacted copolymer as defined in Example 1, (A).

TABLE II Amount of Moi percent Silane, of modified parts by organe- Mixture Sllane weight Adduct unit siloxane (A) Allyltrirnethoxysilane 2.9 (CH3O)3S1CII2CH2CH2(CH3)S1O 41 (13).. Vinyltriethoxysilane. 2.9 (CI'I3CH20)3SlCHZCHZ(CH3)S1O 35 (0) Vinyltriacetoxysilane 2. (1 (CHqCOOMSiCHzCHflCHQSiO 19 (D) Allyltrimethoxysilan A 2.0 (C1130)3S1CH1CH2CH2(CH3)S1O 28 (E) Vinyltn'ethoxysilane 2. O (CILCHZO )3SiCH2CHg(CH3)Sl0 24 (F) 4.0 (CHQCOO)$SiCH2CHZ(CH3)SiO 39 (G) 5.0 icHqC0O)3S1CH2CH(CH3)S1O 49 (H) 5.0 (CHzOhSiCHqCIhCHflCHflSiO T (I) Vinyltrlethoxysilane .t 5.0 (CH3CHZO)3S1CH2CH2(CH3)Slo 60 TABLE IV Amount of M01 percent silane, of modified parts by organe- Mixture Sllane weight Adduct unit siloxane (A) Vinyltriacewxysilane A. 2.9 (CHaCOO)3S1CHzCH-:(CH3]S10 28 }Vinyltriacet0xysilane 2. (J (CH COOhSiCHaC Hz(CH3)SiO 2 (B an 3' Allyltrimethoxysilane 0. 9 (CHQOMSlCHZCHZCHflCH SiO Vinyltriaoetoxysilane 1. 45 (cH3COO)3S1CH2CH2(CH3)S1O 3 (C) and 5 Allyltrimethoxysilane 1. 45 (CH O) S1CH2CH2CH2(CH SiO pinydltriacetoxysilane O. 9 (CH C OO)3S1CH:CH2(CH3)S1O 37 (D) an Allyltrimethoxysilane 2. 0 (CHaOhSiCH2CH2CH2(CH3)S1O E) Allyltrimethoxysilane 2. 9 (CH30 3S1CH2CHZCH2(CH3)S10 41 The silicone elastomer compositions were prepared by mixing on a commercial mixer 100 parts by weight of a methylphenylvinylsiloxy endblocked polydimethylsiloxane having a viscosity of $8,000 cs. at C., 20 parts by weight of a fume silica as defined in Example 1, 1.5 parts by weight of a mixture (A) through (E) as Table III.

TAB LE III Adhesion Aluminum Steel Durom- Tensile Elonga- Tear eter, strength tion at strength Peel Percent Peel Percent Composition Share at break, break Die 13, strength, cohesive strength, cohesive with mixture A p.s.i. percen p.l.i. p.l.i. failure p.11 failure Control 1 1, 080 827 48 25 0 90 (A 27 1, 316 960 90 50 9G 50 29 1, 085 920 49 85 5O 85 50 33 1, 153 793 57 140 100 210 100 83 1. 340 860 53 65 0 30 1, 280 873 49 55 0 130 100 28 1 255 915 183 155 100 155 22 930 980 105 110 130' 100 28 1, 205 930 63 50 55 27 1, 335 935 67 60- 0 1 O0 1 Control was 2.6 parts by weight of the copolymer as defined in (A) above.

defined above and 20 drops of a chloroplatinic acid catalyst. The silicone elastomer was cured for testing both for physical properties and adhesion tested by heating minutes at 150C. The adhesion tests were o snai and x is an integer of from 2 to 3 inclusive, and endcarried out the same as in Example The results were 5 blocked with organosiloxane units selected from the as shown in Table V.

group consisting of trimethylsiloxane units, dimethyl- TABLE V Adhesion Aluminum Steel Durom- Tensile Elonga- Tear eter, strength tion at strength Peel Percent Peel Perce nt Composition Shore at break, break, die B, strength, cohesive strength, cohesive with mixture A p.s.1. percent p.l p.l.i. failure p.l.i. failure That which is claimed is: hydrogensiloxane units and 1. A method of preparing a silicone elastomer metal substrate composite comprising applying to said substrate a composition consisting essentially of (l) a vinyldiorganosiloxy endblocked polydimethylsiloxane having a viscosity of from 1,000 to 100,000 cs. atQ5C. wherein the organic groups of the vinyldiorganosiloxy units are selected from the group consisting of methyl and phenyl, (2) a mixture consisting essentially of (a) an organosiloxane having an average of from 5 to inclusive silicon atoms per molecule, organosiloxane units bonded together through silicon-oxygen-silicon bonds and selected from the group consisting of dimethylsiloxane units and methylhydrogensiloxane units and endblocked with organosiloxane units selected from the group consisting of trimethylsiloxane units and diemthylhydrogensiloxane units, there being present an average of at least three silicon-bonded hydrogen atoms per molecule, and (b) a modified organosiloxane having an average of from six to 21 silicon atoms per molecule, organosiloxane units bonded together through silicon-oxygen-silicon bonds selected from the group consisting of dimethylsiloxane units, methylhydrogensiloxane units and (R0 Si(CH (CH )SiO units wherein R is a monovalent radical selected from the group consisting of methyl, ethyl and (R0) Si(CI-l ),(Cl-l SiO units, there being present an average of at least two silicon-bonded hydrogen atoms per molecule and an average of one silicone unit selected from the group consisting of (RO),, Si(CH (CH )SiO units (R0) Si(Cl-l ,,(Cl-l SiO units, said mixture (2) being present in an amount sufficient to provide at least one silicon-bonded hydrogen atom per vinyl radical in (l) and not more than 10 silicon-bonded hydrogen atoms per vinyl radical in l said mixture having present from 15 to mol percent modified organosiloxane (b) where (a) and (b) are 100 mol percent, and a catalytic amount of a platinum catalyst, thereafter heating the composite above C. for at least 5 minutes whereby a cured silicone elastomer metal substrate the metal substrate is steel.

4. The method in accordance with claim 2 in which the metal substrate is aluminum.

U .S. PATENT OFFICE UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated; November 15, 1973 Patent No. 5,772,066

' William H. Clark and William R. Hays It is certified that errors appear in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

Column 10, line 22, "silicone" should read -siloxane--.

and sealed this 16th day of April 1971;.

(SEAL) Attest:

EDWARD I LFLETCHEEQJR 1 C I IARSHALL LANN Attesting; Officer Commissioner of Patents 

2. The method in accordance with claim 1 in which a filler is present in the composition.
 3. The method in accordance with claim 2 in which the metal substrate is steel.
 4. The method in accordance with claim 2 in which the metal substrate is aluminum. 